Expansible mandrels and chucks and other similar devices for supporting cores for winding webs such as paper, film, foil, metal sheet coils, textiles and the like are well-known in the prior art. In general, such expansible chucks either use mechanical means for obtaining the expansion or pneumatic means which expands flexible or elastic material to engage the interior of the cores. A variety of mechanical expanding chucks are known. Some use screwthread or nut methods to expand movable elements outwardly to engage the core. Others depend upon tension of the web being wound or unwound to activate cam-type elements which accomplish chuck expansion and engagement of the core. The thread and nut devices usually consume significant time to obtain the desired engagement and are not always dependable because the applied torque may vary from application to application. Further, they may not provide a means to follow and continually bear against the core's interior surface should it stretch or move during winding process.
Mechanical expansible chucks which depend upon web tension to activate cam elements are not always dependable because the web tension varies considerably with various types of material being wound; for example, plastic film frequently requires a light web tension which sometimes proves insufficient to activate the cam mechanism. On the other hand, with materials requiring high web tension, a mechanically expansible chuck may become mechanically jammed whereby its removal from the core can be difficult.
Chucks which use pneumatic means for expansion and engagement generally have an elastic element such as a tire or inflatable tube which causes the engagement components to expand outwardly for securing same within the core. Inasmuch as there is normally about a one-sixteenth inch clearance for chuck insertion into the core, the elastic element tends to expand into space offering the least resistance when charged with compressed air and the chuck is sometimes engaged in an eccentric position. This, in turn, causes vibration during the winding process which, in turn, reduces the speed with which the roll can be wound or unwound.
The use of compressed air to cause mechanical engagement of a chuck assembly with the interior of a core is not unknown. For example, U.S. Pat. No. 3,753,570 to A. S. Espasa discloses a locking head wherein air pressure is utilized to move an actuator which, in turn, causes a locking arm to move outwardly and engages the interior of the core.
U.S. Pat. No. 3,997,176 to J. Wyckoff et al is directed to an expansible mandrel wherein a tapered member is moved by a piston and cylinder assembly to expand a plurality of wedge members surrounded by spacer plates and an elastic member.
The instant inventors have previously disclosed expansible core-shafts which utilize fluid pressure for obtaining the desired expansion and securing of the cores. Thus, attention is invited to U.S. Pat. Nos. 4,050,643 of Sept. 27, 1977 and 4,147,312 of Apr. 3, 1979. In such patents, the background and state-of-the-art is discussed and the disclosures in such patents, together with other patent mentioned above, are incorporated by reference into this specification.